Job Ready SQL

Lesson 3Creating Entity‐Relationship Diagrams

Once you've gone through the steps of normalizing a database and determined what tables, fields, and relationships the database should have, it is helpful to create a visual representation of the database structure. This can be done using an entity‐relationship diagram (ERD).

Learning Objectives

By the end of this lesson, learners will be able to:

• Create an ERD that includes the tables, fields, and relationships identified at the end of the database normalization process
• Include appropriate metadata about the database components in the ERD, including primary and foreign keys, data types, and nullability of individual fields

USING ERDs

When discussing an abstract form of a database, the term entity is typically used to reference each object (such as people, things, places, and events) that will be managed in the database. An entity‐relationship diagram (ERD) can be used to represent the entities and the relationships between the entities. Because each final version of an entity will be a table in the completed database, the terms entity and table are often used to mean virtually the same thing, where entity is an abstract representation of the same thing described by a table in a database.

The normalization steps described in the Chapter 2 help you to identify what tables and fields a database will have and how the tables themselves are related to each other. At the end of that process, however, you should create an ERD, ...